1. Technical Field
The present invention relates to an encapsulation device, medical capsules, and an encapsulation method.
2. Related Art
Capsules formed by covering a core substance (core) with a film (shell) have been known. Among the capsules, fine capsules having a particle diameter in micrometer order are referred to as microcapsules (or microspheres and gel beads) and have been developed in recent years. Microcapsules may be imparted with various functions by selecting appropriately the materials for forming the core and the shell. For example, a function of protecting the core from the external environment, a function of controlling the rate of releasing the core to the external environment, and the like may be imparted to the microcapsules, and the microcapsules are currently applied as a functional material to various fields including foods, pharmaceuticals and the like.
As a method for forming the microcapsules, such a method has been known that a core material for forming the core of the capsules and a shell material for forming the shell (both of which materials are in liquid form) are used, and the core material is covered with the shell material, thereby forming the capsules. For example, the following method is proposed (see, for example, JP-A-2005-224647). The shell material having a smaller specific gravity than the core material is floated on the liquid surface of the core material, and the shell material is retained in the form of a liquid film. Bubbles are formed and broken in the vicinity of the interface between the core material and the shell material (immediately beneath the liquid surface of the core material), and by means of pressure formed through the breakage of the bubbles, the core material is discharged toward the liquid film of the shell material with the pressure formed, and the core material is covered and wrapped with the shell material, thereby forming the microcapsules.
The method disclosed in JP-A-2005-224647 facilitates the formation of microcapsules having a shell with a uniform thickness.
Since the method disclosed in JP-A-2005-224647 forms capsules by generating pressure formed through the breakage of the bubbles, however, it is difficult to control precisely the particle diameter of the capsules formed, and thus the method is not suitable for forming capsules with high accuracy. Furthermore, the yield rate of the core material upon forming the capsules may be lowered since the core material is necessarily retained in the form of a liquid film.
JP-A-2005-224647 does not disclose a method of curing the shell after wrapping the core material with the shell material. Accordingly, only capsules having a core material wrapped by a liquid (shell material) may be formed, but capsules having a shell that is cured to suitable hardness may not be formed. The capsules with a liquid shell fail to exhibit sufficiently such functions as protecting the core from the external environment, and thus are limited in application.